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I'm up and running on Ubuntu server with software raid 1 with 2 500GB drives and I'm just trying to test things out.

If I unplug the second drive I'm able to boot in degraded mode but if I unplug the first drive the system is unbootable.

When I went through the install I placed an EFI partition on each drive but it seems like only one was written.

So, I'm looking for a way to make the second drive bootable in the event of a failure. I'm not finding much in the way of software raid with EFI.

Also, it doesn't look like this mobo has a BIOS mode so I can't fall back to that.

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I'm not surprised that the installer only put GRUB on one drive's EFI partition. You'll need to copy the files to the other drives' EFI partitions yourself. You'll probably also want to use efibootmgr to create boot menu entries for those other copies of GRUB, so that you'll have them as options to boot from. (Each entry refers to a specific partition on a specific drive; I don't think you can have one that searches multiple drives)

You could put an EFI partition on a flash drive, install GRUB on that, create a boot entry for it, and leave it permanently plugged into the machine. That way you don't depend on either drive for your bootloader.

Even if you just have GRUB on the first disk, you could put the EFI Shell on a flash drive, boot from that, and use it to invoke GRUB from either disk's EFI partition. So even if you don't do anything special now, you'll be able to get the machine booted with some manual intervention if that first disk fails.

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I just had to mount the second efi partition which in my case was "/dev/sdb1" and copy over the EFI directory from the primary efi partition which gets auto-mounted to /boot/efi/. I could add a separate boot entry but it works the way I have it and this is just disaster recovery anyway. Thanks. –  kjs3 Jul 26 '12 at 21:30
    
What about just RAIDing the EFI system partitions on the multiple disks? spinics.net/lists/raid/msg45793.html –  CMCDragonkai Jul 2 at 7:33
    
That might work, as long as the RAID is set up in such a way that each individual partition looks like an ordinary valid filesystem to the EFI (which isn't aware of the RAID). Linux software RAID1 using superblock format 1.0 (superblock at the end) may work. –  Wyzard Jul 2 at 12:22
    
But as I understand it, the entries in the EFI boot menu — the information that tells it to run grubx64.efi from a particular directory in the EFI system partition — include the GUID of the partition that contains the file. So even if you have identical partitions on two different disks, the EFI will only try to boot from one of them. You could try giving the partitions the same GUID, but that might cause further problems since they're expected to be unique. –  Wyzard Jul 2 at 12:25
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